Computed tomography (CT) is an imaging technique that is widely used in the medical field. In general, an x-ray source and a detector are positioned on opposite sides of a patient. The x-ray source generates and directs an x-ray beam towards the patient, while the detector measures the x-ray absorption along different transmission paths. By taking many readings from multiple angles around the patient, relatively large amounts of data can be accumulated. That data can then be analyzed and processed to construct a three-dimensional representation of the patient's insides.
While performing CT, a filter is generally placed between the patient and the x-ray source in order to, for example, reduce the intensity of the x-ray beam or shape the x-ray beam, thereby reducing the radiation dose experienced by the patient. One class of filter (e.g., beam hardening filters) may be used to change the beam's energy spectrum, and another class of filter (e.g., shape filters) may be used to change the beam's shape. Within each class of filter, there may be a number of different filters—that is, there may be a number of different beam hardening filters, and a number of different shape filters. Different filters are selected and used depending on, for example, the types of procedures to be performed.
In one conventional implementation, a filter is selected and manually placed in a fixed position inside the beam path. To change the filter to a different one, an operator must enter the treatment room, manually remove the installed filter, and insert the new filter. Consequently, the process of setting up a different filter, including alignment and perhaps calibration, can take a relatively long time. From the patient's perspective, the wait may be both inconvenient and uncomfortable.
In another conventional implementation, a motor is used to move a filter into a filtering position in the beam path. However, if a different filter is to be used, an operator must still enter the treatment room and manually replace that filter with another in a manner similar to that just described.
There are other types of conventional implementations in use, but in general those implementations share the problems described above.